Method for bit-byte synchronization in sampling a data string

Abstract

Bit and byte synchronization for sampling and decoding a data string is provided a single data field u. The data string x has pre-pended to it a short string of 1s (ones), followed by u to yield a string y= . . . 1111, u, x. The string is pre-coded by convolution with 1/(1⊕D 2 ). PRML-sampling of y starts at an initial phase, and vectors are obtained from that string by sampling at pre-selected phases following the initial sampling point. The vectors of y are compared with vectors corresponding to PRML samples of an initial set of bits in u obtained at predetermined phases. The pair of y, u vectors exhibiting the minimum Euclidian distance yields a sampling correction value by which the initial sampling phase is corrected and a new initial sampling point preceding x is determined. Here, bit and byte synchronization have been achieved and sampling of x proceeds at the corrected phase, from the new initial sampling point.

1. A method for synchronization of data detection with a stream of encoded digital data, comprising:
 establishing u where u is a predetermined bit-byte synchronization pattern of bits; 
 obtaining a plurality of vectors u j  by sampling u at predetermined PRML (partial-response, maximum-likelihood) phases; 
 receiving a string of digital data y, where y =. . . 1111, u, x, and x is a string of PRML-encoded data; 
 producing from y a string of samples v at sampling points f, f+1, f+2, . . . before the start of u; 
 determining a plurality of Euclidian distances d i,j  between a sequence v i  of samples and each of the vectors u j ; 
 finding a minimum Euclidian distance of the plurality of Euclidian distances; 
 calculating a correction value based on the minimum Euclidian distance; 
 correcting the sampling points by the correction value; and 
 sampling y at the corrected sampling points. 
 
     
     
       2. The method of  claim 1 , wherein the string of digital data is a precoded string of digital data (1/(1⊕D 2 ))·y, where ⊕ denotes modulo-2 addition. 
     
     
       3. The method of  claim 2 , wherein the determining step includes:
 if a first of the plurality of Euclidian distances exceeds a predetermined threshold, incrementing i and repeating the determining step; otherwise, 
 denominating the first Euclidian distance as a first minimum Euclidian distance m i ; and then: 
 i. finding the next minimum Euclidian distance m i+1  following the first Euclidian distance; and 
 ii. if m i >m i+1  incrementing i and repeating step i; otherwise 
 iii. denominating m i  as the minimum Euclidian distance of the plurality of Euclidian distances. 
 
     
     
       4. The method of  claim 3 , wherein:
 the calculating step includes denominating J 0  such that the minimum Euclidian distance of the plurality of Euclidian distances is m i =d ij0 ; and 
 the correcting step includes correcting f by f←f−(j 0 /8) such that the corrected sampling points are f+i+n, f+i+(n+1), f+i+(n+2). 
 
     
     
       5. The method of  claim 4 , further including:
 producing a sampled sequence w=w 0 , w 1 , w 2 , . . . by sampling the pre-coded string at the corrected sampling points; and 
 applying maximum likelihood decoding to w to obtain an estimate of x. 
 
     
     
       6. The method of  claim 2 , wherein the determining step includes:
 if a first of the plurality of Euclidian distances exceeds a predetermined threshold, incrementing i and repeating the determining step; otherwise, 
 performing the finding step by assembling a group of minimal Euclidian distances in the plurality of Euclidian distances. 
 
     
     
       7. The method of  claim 6 , wherein:
 the calculating step includes interpolating among the group of minimal Euclidian distances, and denominating the result, r, of the interpolating step as the minimum Euclidian distance of the plurality of Euclidian distances, 
 the correcting step includes correcting f by f←f−(r−1) such that the corrected sampling points are f+i+n, f+i+(n+1), f+i+(n+2). 
 
     
     
       8. The method of  claim 7 , further including:
 producing a sampled sequence w=w 0 , w 1 , w 2 , . . . by sampling the pre-coded string at the corrected sampling points; and 
 applying maximum likelihood decoding to w to obtain an estimate of x. 
 
     
     
       9. The method of  claim 7 , wherein the calculating step includes:
 testing values in the group of minimal Euclidian distances to determine a range of minimal Euclidian distances; 
 if the range exceeds a predetermined value, interpolating among the group of minimal Euclidian distances, and denominating the result, r, of the interpolating step as the minimum Euclidian distance of the plurality of Euclidian distances; otherwise 
 interpolating among selected minimal Euclidian distances in the group of minimal Euclidian distances, and denominating the result, r, of the interpolating step as the minimum Euclidian distance of the plurality of Euclidian distances. 
 
     
     
       10. The method of step  9 , wherein the correcting step includes correcting f by 
       f←f−(r−1) such that the corrected sampling points are f+i+n, f+i+(n+1), f+i+(n +2). 
     
     
       11. The method of  claim 10 , further including:
 producing a sampled sequence w=w 0 , w 1 , w 2 , . . . by sampling the pre-coded string at the corrected sampling points; and 
 applying maximum likelihood decoding to w to obtain an estimate of x. 
 
     
     
       12. In a data storage apparatus, a data synchronization procedure comprising:
 establishing u, where u is a predetermined bit-byte synchronization pattern of bits; 
 obtaining a plurality of vectors u j  by sampling u at predetermined PRML (partial-response, maximum-likelihood) phases; 
 receiving a string of digital data for storage, where the string is . . . 1111, u, x, and x is a string of PRML-encoded data; 
 pre-coding the string of digital data with (1/(1⊕D 2 )) to produce a pre-coded string y, where ⊕ denotes modulo-2 addition; 
 storing y on a data storage medium in the storage apparatus; 
 reading y from the storage medium as a string of samples v at sampling points f, f+1, 
 f+2, . . . before the start of u; 
 determining a plurality of Euclidian distances d ij  between a sequence v i  of samples and each of the vectors u j ; 
 finding a minimum Euclidian distance of the plurality of Euclidian distances; 
 calculating a correction value based on the minimum Euclidian distance; 
 correcting the sampling points by the correction value; and 
 sampling y at the corrected sampling points. 
 
     
     
       13. The procedure of  claim 12 , further including:
 producing a sampled sequence w=w 0 , w 1 , w 2 , . . . by sampling y at the corrected sampling points; and 
 applying maximum likelihood decoding to w to obtain an estimate of x. 
 
     
     
       14. The procedure of  claim 13 , wherein the determining step includes:
 if a first of the plurality of Euclidian distances exceeds a predetermined threshold, incrementing i and repeating the determining step; otherwise, 
 denominating the first Euclidian distance as a first minimum Euclidian distance m i ; and then: 
 i. finding the next minimum Euclidian distance m i+1  following the first Euclidian distance; and 
 ii. if m i >m i+1  incrementing i and repeating step i; otherwise 
 iii. denominating m i  as the minimum Euclidian distance of the plurality of Euclidian distances. 
 
     
     
       15. The procedure of  claim 14 , wherein:
 the calculating step includes denominating J 0  such that the minimum Euclidian distance of the plurality of Euclidian distances is m i =d i,j0 ; and 
 the correcting step includes correcting f by f←f−(j 0 /8) such that the corrected sampling points are f+i+n, f+i+(n+1), f+i+(n+2). 
 
     
     
       16. The procedure of  claim 13 , wherein the determining step includes:
 if a first of the plurality of Euclidian distances exceeds a predetermined threshold, incrementing i and repeating the determining step; otherwise, 
 performing the finding step by assembling a group of minimal Euclidian distances in the plurality of Euclidian distances. 
 
     
     
       17. The procedure of  claim 16 , wherein:
 the calculating step includes interpolating among the group of minimal Euclidian distances, and denominating the result, r, of the interpolating step as the minimum Euclidian distance of the plurality of Euclidian distances, 
 the correcting step includes correcting f by f←f−(r+1) such that the corrected sampling points are f+i+n, f+i+(n+1), f+i+(n+2). 
 
     
     
       18. The procedure of  claim 17 , wherein the calculating step includes:
 testing values in the group of minimal Euclidian distances to determine a range of minimal Euclidian distances; 
 if the range exceeds a predetermined value, interpolating among the group of minimal Euclidian distances, and denominating the result, r, of the interpolating step as the minimum Euclidian distance of the plurality of Euclidian distances; otherwise 
 interpolating among selected minimal Euclidian distances in the group of minimal Euclidian distances, and denominating the result, r, of the interpolating step as the minimum Euclidian distance of the plurality of Euclidian distances. 
 
     
     
       19. The procedure of  claim 18 , wherein the correcting step includes correcting f by 
       f←f−(r−1) such that the corrected sampling points are f+i+n, f+i+(n+1), f+i+(n +2). 
     
     
       20. The procedure of  claims 15 ,  17 , and  19 , wherein n=20.